Add a simple cache for objects stored in etcd.

pkg/master/master_test.go

@@ -30,7 +30,8 @@ func TestGetServersToValidate(t *testing.T) {
 	config := Config{}
 	fakeClient := tools.NewFakeEtcdClient(t)
 	fakeClient.Machines = []string{"http://machine1:4001", "http://machine2", "http://machine3:4003"}
-	config.EtcdHelper = tools.EtcdHelper{fakeClient, latest.Codec, nil}
+	config.EtcdHelper = tools.NewEtcdHelper(fakeClient, latest.Codec)
+	config.EtcdHelper.Versioner = nil
 
 	master.nodeRegistry = registrytest.NewMinionRegistry([]string{"node1", "node2"}, api.NodeResources{})
 

pkg/tools/etcd_helper.go

@@ -24,6 +24,7 @@ import (
 	"net/http"
 	"os/exec"
 	"reflect"
+	"sync"
 
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/conversion"
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/runtime"
@@ -38,6 +39,15 @@ type EtcdHelper struct {
 	Codec  runtime.Codec
 	// optional, no atomic operations can be performed without this interface
 	Versioner EtcdVersioner
+
+	// We cache objects stored in etcd. For keys we use Node.ModifiedIndex which is equivalent
+	// to resourceVersion.
+	// This depends on etcd's indexes being globally unique across all objects/types. This will
+	// have to revisited if we decide to do things like multiple etcd clusters, or etcd will
+	// support multi-object transaction that will result in many objects with the same index.
+	// Number of entries stored in the cache is controlled by maxEtcdCacheEntries constant.
+	cache map[uint64]interface{}
+	mutex sync.RWMutex
 }
 
 // NewEtcdHelper creates a helper that works against objects that use the internal
@@ -47,6 +57,7 @@ func NewEtcdHelper(client EtcdGetSet, codec runtime.Codec) EtcdHelper {
 		Client:    client,
 		Codec:     codec,
 		Versioner: APIObjectVersioner{},
+		cache:     make(map[uint64]interface{}),
 	}
 }
 
@@ -116,19 +127,70 @@ func (h *EtcdHelper) decodeNodeList(nodes []*etcd.Node, slicePtr interface{}) er
 			}
 			continue
 		}
-		obj := reflect.New(v.Type().Elem())
-		if err := h.Codec.DecodeInto([]byte(node.Value), obj.Interface().(runtime.Object)); err != nil {
-			return err
-		}
-		if h.Versioner != nil {
-			// being unable to set the version does not prevent the object from being extracted
-			_ = h.Versioner.UpdateObject(obj.Interface().(runtime.Object), node)
+		if obj, found := h.getFromCache(node.ModifiedIndex); found {
+			v.Set(reflect.Append(v, reflect.ValueOf(obj)))
+		} else {
+			obj := reflect.New(v.Type().Elem())
+			if err := h.Codec.DecodeInto([]byte(node.Value), obj.Interface().(runtime.Object)); err != nil {
+				return err
+			}
+			if h.Versioner != nil {
+				// being unable to set the version does not prevent the object from being extracted
+				_ = h.Versioner.UpdateObject(obj.Interface().(runtime.Object), node)
+			}
+			v.Set(reflect.Append(v, obj.Elem()))
+			if node.ModifiedIndex != 0 {
+				h.addToCache(node.ModifiedIndex, obj.Interface())
+			}
 		}
-		v.Set(reflect.Append(v, obj.Elem()))
 	}
 	return nil
 }
 
+// etcdCache defines interface used for caching objects stored in etcd. Objects are keyed by
+// their Node.ModifiedIndex, which is unique across all types.
+// All implementations must be thread-safe.
+type etcdCache interface {
+	getFromCache(index uint64) (interface{}, bool)
+	addToCache(index uint64, obj interface{})
+}
+
+const maxEtcdCacheEntries int = 100000
+
+func (h *EtcdHelper) getFromCache(index uint64) (interface{}, bool) {
+	var obj interface{}
+	func() {
+		h.mutex.RLock()
+		defer h.mutex.RUnlock()
+		obj = h.cache[index]
+	}()
+	if obj != nil {
+		// We should not return the object itself to avoid poluting the cache if someone
+		// modifies returned values.
+		objCopy, err := conversion.DeepCopy(obj)
+		if err != nil {
+			glog.Errorf("Error during DeepCopy of cached object: %q", err)
+			return nil, false
+		}
+		return objCopy, true
+	} else {
+		return nil, false
+	}
+}
+
+func (h *EtcdHelper) addToCache(index uint64, obj interface{}) {
+	h.mutex.Lock()
+	defer h.mutex.Unlock()
+	h.cache[index] = obj
+	if len(h.cache) > maxEtcdCacheEntries {
+		var randomKey uint64
+		for randomKey = range h.cache {
+			break
+		}
+		delete(h.cache, randomKey)
+	}
+}
+
 // ExtractToList works on a *List api object (an object that satisfies the runtime.IsList
 // definition) and extracts a go object per etcd node into a slice with the resource version.
 func (h *EtcdHelper) ExtractToList(key string, listObj runtime.Object) error {

pkg/tools/etcd_helper_test.go

@@ -169,7 +169,7 @@ func TestExtractToListAcrossDirectories(t *testing.T) {
 								Key:           "/baz",
 								Value:         getEncodedPod("baz"),
 								Dir:           false,
-								ModifiedIndex: 1,
+								ModifiedIndex: 3,
 							},
 						},
 					},
@@ -194,7 +194,7 @@ func TestExtractToListAcrossDirectories(t *testing.T) {
 		Items: []api.Pod{
 			// We expect list to be sorted by directory (e.g. namespace) first, then by name.
 			{
-				ObjectMeta: api.ObjectMeta{Name: "baz", ResourceVersion: "1"},
+				ObjectMeta: api.ObjectMeta{Name: "baz", ResourceVersion: "3"},
 				Spec: api.PodSpec{
 					RestartPolicy: api.RestartPolicyAlways,
 					DNSPolicy:     api.DNSClusterFirst,
@@ -470,7 +470,8 @@ func TestSetObjWithVersion(t *testing.T) {
 func TestSetObjWithoutResourceVersioner(t *testing.T) {
 	obj := &api.Pod{ObjectMeta: api.ObjectMeta{Name: "foo"}}
 	fakeClient := NewFakeEtcdClient(t)
-	helper := EtcdHelper{fakeClient, testapi.Codec(), nil}
+	helper := NewEtcdHelper(fakeClient, testapi.Codec())
+	helper.Versioner = nil
 	returnedObj := &api.Pod{}
 	err := helper.SetObj("/some/key", obj, returnedObj, 3)
 	if err != nil {
@@ -496,7 +497,8 @@ func TestSetObjWithoutResourceVersioner(t *testing.T) {
 func TestSetObjNilOutParam(t *testing.T) {
 	obj := &api.Pod{ObjectMeta: api.ObjectMeta{Name: "foo"}}
 	fakeClient := NewFakeEtcdClient(t)
-	helper := EtcdHelper{fakeClient, testapi.Codec(), nil}
+	helper := NewEtcdHelper(fakeClient, testapi.Codec())
+	helper.Versioner = nil
 	err := helper.SetObj("/some/key", obj, nil, 3)
 	if err != nil {
 		t.Errorf("Unexpected error %#v", err)

pkg/tools/etcd_helper_watch.go

@@ -71,7 +71,7 @@ func ParseWatchResourceVersion(resourceVersion, kind string) (uint64, error) {
 // watch.Interface. resourceVersion may be used to specify what version to begin
 // watching (e.g., for reconnecting without missing any updates).
 func (h *EtcdHelper) WatchList(key string, resourceVersion uint64, filter FilterFunc) (watch.Interface, error) {
-	w := newEtcdWatcher(true, exceptKey(key), filter, h.Codec, h.Versioner, nil)
+	w := newEtcdWatcher(true, exceptKey(key), filter, h.Codec, h.Versioner, nil, h)
 	go w.etcdWatch(h.Client, key, resourceVersion)
 	return w, nil
 }
@@ -80,7 +80,7 @@ func (h *EtcdHelper) WatchList(key string, resourceVersion uint64, filter Filter
 // API objects and sent down the returned watch.Interface.
 // Errors will be sent down the channel.
 func (h *EtcdHelper) Watch(key string, resourceVersion uint64, filter FilterFunc) (watch.Interface, error) {
-	w := newEtcdWatcher(false, nil, filter, h.Codec, h.Versioner, nil)
+	w := newEtcdWatcher(false, nil, filter, h.Codec, h.Versioner, nil, h)
 	go w.etcdWatch(h.Client, key, resourceVersion)
 	return w, nil
 }
@@ -102,7 +102,7 @@ func (h *EtcdHelper) Watch(key string, resourceVersion uint64, filter FilterFunc
 //
 // Errors will be sent down the channel.
 func (h *EtcdHelper) WatchAndTransform(key string, resourceVersion uint64, transform TransformFunc) watch.Interface {
-	w := newEtcdWatcher(false, nil, Everything, h.Codec, h.Versioner, transform)
+	w := newEtcdWatcher(false, nil, Everything, h.Codec, h.Versioner, transform, h)
 	go w.etcdWatch(h.Client, key, resourceVersion)
 	return w
 }
@@ -142,14 +142,16 @@ type etcdWatcher struct {
 
 	// Injectable for testing. Send the event down the outgoing channel.
 	emit func(watch.Event)
+
+	cache etcdCache
 }
 
 // watchWaitDuration is the amount of time to wait for an error from watch.
 const watchWaitDuration = 100 * time.Millisecond
 
 // newEtcdWatcher returns a new etcdWatcher; if list is true, watch sub-nodes.  If you provide a transform
 // and a versioner, the versioner must be able to handle the objects that transform creates.
-func newEtcdWatcher(list bool, include includeFunc, filter FilterFunc, encoding runtime.Codec, versioner EtcdVersioner, transform TransformFunc) *etcdWatcher {
+func newEtcdWatcher(list bool, include includeFunc, filter FilterFunc, encoding runtime.Codec, versioner EtcdVersioner, transform TransformFunc, cache etcdCache) *etcdWatcher {
 	w := &etcdWatcher{
 		encoding:     encoding,
 		versioner:    versioner,
@@ -162,6 +164,7 @@ func newEtcdWatcher(list bool, include includeFunc, filter FilterFunc, encoding
 		etcdStop:     make(chan bool),
 		outgoing:     make(chan watch.Event),
 		userStop:     make(chan struct{}),
+		cache:        cache,
 	}
 	w.emit = func(e watch.Event) { w.outgoing <- e }
 	go w.translate()
@@ -253,6 +256,10 @@ func (w *etcdWatcher) translate() {
 }
 
 func (w *etcdWatcher) decodeObject(node *etcd.Node) (runtime.Object, error) {
+	if obj, found := w.cache.getFromCache(node.ModifiedIndex); found {
+		return obj.(runtime.Object), nil
+	}
+
 	obj, err := w.encoding.Decode([]byte(node.Value))
 	if err != nil {
 		return nil, err
@@ -274,6 +281,9 @@ func (w *etcdWatcher) decodeObject(node *etcd.Node) (runtime.Object, error) {
 		}
 	}
 
+	if node.ModifiedIndex != 0 {
+		w.cache.addToCache(node.ModifiedIndex, obj)
+	}
 	return obj, nil
 }
 

pkg/tools/etcd_helper_watch_test.go

@@ -31,6 +31,16 @@ import (
 
 var versioner = APIObjectVersioner{}
 
+// Implements etcdCache interface as empty methods (i.e. does not cache any objects)
+type fakeEtcdCache struct{}
+
+func (f *fakeEtcdCache) getFromCache(index uint64) (interface{}, bool) {
+	return nil, false
+}
+
+func (f *fakeEtcdCache) addToCache(index uint64, obj interface{}) {
+}
+
 func TestWatchInterpretations(t *testing.T) {
 	codec := latest.Codec
 	// Declare some pods to make the test cases compact.
@@ -114,7 +124,7 @@ func TestWatchInterpretations(t *testing.T) {
 
 	for name, item := range table {
 		for _, action := range item.actions {
-			w := newEtcdWatcher(true, nil, firstLetterIsB, codec, versioner, nil)
+			w := newEtcdWatcher(true, nil, firstLetterIsB, codec, versioner, nil, &fakeEtcdCache{})
 			emitCalled := false
 			w.emit = func(event watch.Event) {
 				emitCalled = true
@@ -152,7 +162,7 @@ func TestWatchInterpretations(t *testing.T) {
 }
 
 func TestWatchInterpretation_ResponseNotSet(t *testing.T) {
-	w := newEtcdWatcher(false, nil, Everything, codec, versioner, nil)
+	w := newEtcdWatcher(false, nil, Everything, codec, versioner, nil, &fakeEtcdCache{})
 	w.emit = func(e watch.Event) {
 		t.Errorf("Unexpected emit: %v", e)
 	}
@@ -166,7 +176,7 @@ func TestWatchInterpretation_ResponseNotSet(t *testing.T) {
 func TestWatchInterpretation_ResponseNoNode(t *testing.T) {
 	actions := []string{"create", "set", "compareAndSwap", "delete"}
 	for _, action := range actions {
-		w := newEtcdWatcher(false, nil, Everything, codec, versioner, nil)
+		w := newEtcdWatcher(false, nil, Everything, codec, versioner, nil, &fakeEtcdCache{})
 		w.emit = func(e watch.Event) {
 			t.Errorf("Unexpected emit: %v", e)
 		}
@@ -180,7 +190,7 @@ func TestWatchInterpretation_ResponseNoNode(t *testing.T) {
 func TestWatchInterpretation_ResponseBadData(t *testing.T) {
 	actions := []string{"create", "set", "compareAndSwap", "delete"}
 	for _, action := range actions {
-		w := newEtcdWatcher(false, nil, Everything, codec, versioner, nil)
+		w := newEtcdWatcher(false, nil, Everything, codec, versioner, nil, &fakeEtcdCache{})
 		w.emit = func(e watch.Event) {
 			t.Errorf("Unexpected emit: %v", e)
 		}
@@ -205,7 +215,7 @@ func TestWatchEtcdError(t *testing.T) {
 	fakeClient := NewFakeEtcdClient(t)
 	fakeClient.expectNotFoundGetSet["/some/key"] = struct{}{}
 	fakeClient.WatchImmediateError = fmt.Errorf("immediate error")
-	h := EtcdHelper{fakeClient, codec, versioner}
+	h := NewEtcdHelper(fakeClient, codec)
 
 	watching, err := h.Watch("/some/key", 4, Everything)
 	if err != nil {
@@ -233,7 +243,7 @@ func TestWatch(t *testing.T) {
 	codec := latest.Codec
 	fakeClient := NewFakeEtcdClient(t)
 	fakeClient.expectNotFoundGetSet["/some/key"] = struct{}{}
-	h := EtcdHelper{fakeClient, codec, versioner}
+	h := NewEtcdHelper(fakeClient, codec)
 
 	watching, err := h.Watch("/some/key", 0, Everything)
 	if err != nil {
@@ -406,7 +416,7 @@ func TestWatchEtcdState(t *testing.T) {
 		for key, value := range testCase.Initial {
 			fakeClient.Data[key] = value
 		}
-		h := EtcdHelper{fakeClient, codec, versioner}
+		h := NewEtcdHelper(fakeClient, codec)
 		watching, err := h.Watch("/somekey/foo", testCase.From, Everything)
 		if err != nil {
 			t.Fatalf("Unexpected error: %v", err)
@@ -477,7 +487,7 @@ func TestWatchFromZeroIndex(t *testing.T) {
 	for k, testCase := range testCases {
 		fakeClient := NewFakeEtcdClient(t)
 		fakeClient.Data["/some/key"] = testCase.Response
-		h := EtcdHelper{fakeClient, codec, versioner}
+		h := NewEtcdHelper(fakeClient, codec)
 
 		watching, err := h.Watch("/some/key", 0, Everything)
 		if err != nil {
@@ -537,7 +547,7 @@ func TestWatchListFromZeroIndex(t *testing.T) {
 			EtcdIndex: 3,
 		},
 	}
-	h := EtcdHelper{fakeClient, codec, versioner}
+	h := NewEtcdHelper(fakeClient, codec)
 
 	watching, err := h.WatchList("/some/key", 0, Everything)
 	if err != nil {
@@ -575,7 +585,7 @@ func TestWatchListIgnoresRootKey(t *testing.T) {
 	pod := &api.Pod{ObjectMeta: api.ObjectMeta{Name: "foo"}}
 
 	fakeClient := NewFakeEtcdClient(t)
-	h := EtcdHelper{fakeClient, codec, versioner}
+	h := NewEtcdHelper(fakeClient, codec)
 
 	watching, err := h.WatchList("/some/key", 1, Everything)
 	if err != nil {
@@ -626,7 +636,7 @@ func TestWatchFromNotFound(t *testing.T) {
 			ErrorCode: 100,
 		},
 	}
-	h := EtcdHelper{fakeClient, codec, versioner}
+	h := NewEtcdHelper(fakeClient, codec)
 
 	watching, err := h.Watch("/some/key", 0, Everything)
 	if err != nil {
@@ -652,7 +662,7 @@ func TestWatchFromOtherError(t *testing.T) {
 			ErrorCode: 101,
 		},
 	}
-	h := EtcdHelper{fakeClient, codec, versioner}
+	h := NewEtcdHelper(fakeClient, codec)
 
 	watching, err := h.Watch("/some/key", 0, Everything)
 	if err != nil {
@@ -683,7 +693,7 @@ func TestWatchFromOtherError(t *testing.T) {
 
 func TestWatchPurposefulShutdown(t *testing.T) {
 	fakeClient := NewFakeEtcdClient(t)
-	h := EtcdHelper{fakeClient, codec, versioner}
+	h := NewEtcdHelper(fakeClient, codec)
 	fakeClient.expectNotFoundGetSet["/some/key"] = struct{}{}
 
 	// Test purposeful shutdown